When we have a weak reference to a symbol defined in an
as-needed library, and that library ends up not-needed, gold
simply clears the version information in the symbol table, even
if the symbol could have been resolved by a needed library later
in the link order. This results in a loss of version information,
which can cause the program to bind to the wrong version at run
time.
This patch lets a dynamic definition override an earlier one if
the earlier one is from a not-needed library, so that we can
retain the version information from the binding to the needed
library. In order to do that, the tracking of needed/not-needed
had to be moved up to symbol resolution time, instead of during
Symbol_table::set_dynsym_indexes().
In cases where we still end up discarding version information,
I've added a warning.
For the original problem report and discussion, see:
https://stackoverflow.com/questions/50751421/undefined-behavior-in-shared-lib-using-libpthread-but-not-having-it-in-elf-as-d
gold/
* resolve.cc (Symbol_table::resolve): Rename tobinding to
orig_tobinding. Call set_is_needed() for objects that resolve
non-weak references.
(Symbol_table::should_override): Allow a dynamic definition to
override an earlier one in a not-needed library.
* symtab.cc (Symbol_table::set_dynsym_indexes): Remove separate
processing for as-needed symbols. Add warning when discarding
version informatin.
* testsuite/Makefile.am (weak_as_needed): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/weak_as_needed.sh: New test script.
* testsuite/weak_as_needed_a.c: New source file.
* testsuite/weak_as_needed_b.c: New source file.
* testsuite/weak_as_needed_b.script: New version script.
* testsuite/weak_as_needed_c.c: New source file.
* testsuite/weak_as_needed_c.script: New version script.
This implements the special __tls_get_addr_opt call stub for powerpc
gold that returns __thread variable addresses without actually making
a call to __tls_get_addr in most cases. Shared libraries that are
loaded at program load time (ie. dlopen is not used) have a known
layout for their __thread variables, and thus DTPMOD64/DPTREL64 pairs
describing those variables can be set up by ld.so for the
__tls_get_addr_opt call stub fast exit.
Ref https://sourceware.org/ml/libc-alpha/2015-03/msg00626.html
I really, really wish I'd used a differently versioned __tls_get_addr
symbol than the base symbol to indicate glibc support for the
optimized call, rather than having glibc export __tls_get_addr_opt. A
lot of the messing around here, flipping symbols from __tls_get_addr
to __tls_get_addr_opt, is caused by that decision. About the only
benefit is that a user can see at a glance that their disassembled
code is calling __tls_get_addr via the fancy call stub.. Anyway, we
need references to __tls_get_addr to seem like they were to
__tls_get_addr_opt, and in cases like the tsan interceptor, a
definition of __tls_get_addr to seem like one of __tls_get_addr_opt
as well. That's the reason for Symbol::clear_in_reg and
Symbol_table::clone, and why symbols are substituted in Scan::global
and other places dealing with dynamic linking.
elfcpp/
* elfcpp.h (DT_PPC_OPT): Define.
* powerpc.h (PPC_OPT_TLS): Define.
gold/
* options.h (tls_get_addr_optimize): New option.
* symtab.h (Symbol::clear_in_reg, clone): New functions.
(Sized_symbol::clone): New function.
(Symbol_table::clone): New function.
* resolve.cc (Symbol::clone, Sized_symbol::clone): New functions.
* powerpc.cc (Target_powerpc::has_tls_get_addr_opt_,
tls_get_addr_, tls_get_addr_opt_): New vars.
(Target_powerpc::tls_get_addr_opt, tls_get_addr,
is_tls_get_addr_opt, replace_tls_get_addr,
set_has_tls_get_addr_opt, stk_linker): New functions.
(Target_powerpc::Track_tls::maybe_skip_tls_get_addr_call): Add
target param. Update callers. Compare symbols rather than names.
(Target_powerpc::do_define_standard_symbols): Init tls_get_addr_
and tls_get_addr_opt_.
(Target_powerpc::Branch_info::mark_pltcall): Translate tls_get_addr
sym to tls_get_addr_opt.
(Target_powerpc::Branch_info::make_stub): Likewise.
(Stub_table::define_stub_syms): Likewise.
(Target_powerpc::Scan::global): Likewise.
(Target_powerpc::Relocate::relocate): Likewise.
(add_3_12_2, add_3_12_13, bctrl, beqlr, cmpdi_11_0, cmpwi_11_0,
ld_11_1, ld_11_3, ld_12_3, lwz_11_3, lwz_12_3, mr_0_3, mr_3_0,
mtlr_11, std_11_1): New constants.
(Stub_table::eh_frame_added_): Delete.
(Stub_table::tls_get_addr_opt_bctrl_, plt_fde_len_, plt_fde_): New vars.
(Stub_table::init_plt_fde): New functions.
(Stub_table::add_eh_frame, replace_eh_frame): Move definition out
of line. Init and use plt_fde_.
(Stub_table::plt_call_size): Return size for tls_get_addr stub.
Extract alignment code to..
(Stub_table::plt_call_align): ..this new function. Adjust all callers.
(Stub_table::add_plt_call_entry): Set has_tls_get_addr_opt and
tls_get_addr_opt_bctrl, and align after that.
(Stub_table::do_write): Write out tls_get_addr stub.
(Target_powerpc::do_finalize_sections): Emit DT_PPC_OPT
PPC_OPT_TLS/PPC64_OPT_TLS bit.
(Target_powerpc::Relocate::relocate): Don't check for or modify
nop following bl for tls_get_addr stub.
On 64-bit targets there is a 32-bit hole in symbol->u_, and another
due to symbol flags exceeding 32 bits. By splitting the union,
the total size of the class reduces by one 64-bit word.
* symtab.h (Symbol): Split u_ into u1_ and u2_. Adjust accessors
to suit. Move plt_offset_ before got_offsets_.
* symtab.cc (Symbol::init_fields): Adjust for union change.
(Symbol::init_base_output_data): Likewise.
(Symbol::init_base_output_segment): Likewise.
(Symbol::allocate_base_common): Likewise.
(Symbol::output_section): Likewise.
(Symbol::set_output_section): Likewise.
(Symbol::set_output_segment): Likewise.
* resolve.cc (Symbol::override_base): Likewise.
(Symbol::override_base_with_special): Likewise.
This patch provides a flag for PowerPC64 ELFv2 use in class Symbol,
and modifies Sized_target::resolve to return whether the symbol has
been resolved. If not, normal processing continues. I use this for
PowerPC64 ELFv2 to keep track of whether a symbol has any definition
with non-zero localentry, in order to disable --plt-localentry for
that symbol.
PR 21847
* powerpc.cc (Target_powerpc::is_elfv2_localentry0): Test
non_zero_localentry.
(Target_powerpc::resolve): New function.
(powerpc_info): Set has_resolve for 64-bit.
* target.h (Sized_target::resolve): Return bool.
* resolve.cc (Symbol_table::resolve): Continue with normal
processing when target resolve returns false.
* symtab.h (Symbol::non_zero_localentry, set_non_zero_localentry):
New accessors.
(Symbol::non_zero_localentry_): New flag bit.
* symtab.cc (Symbol::init_fields): Init non_zero_localentry_.
The previous commit to fix PR gold/18886 converted STT_IFUNC
to STT_FUNC when resolving to a symbol defined in a shared library.
This leads to an internal error if the shared library symbol is
seen first, as we do not convert the symbol at all.
We need to override the STT_IFUNC in add_from_dynobj() instead of
in override_base().
gold/
PR gold/18930
PR gold/18886
* resolve.cc (Symbol::override_base): Don't convert IFUNC symbols here.
* symtab.cc (Symbol_table::add_from_dynobj): Convert them here instead.
Turn IFUNC symbols from shared libraries into normal FUNC symbols when
we are resolving symbol references, instead of when we are writing out
the symbol table.
PR gold/18886
* resolve.cc (Symbol::override_base): Turn IFUNC symbols from
shared libraries into normal FUNC symbols.
* symtab.cc (Symbol_table::sized_write_symbol): Assert IFUNC
symbols aren't from shared libraries.
If a symbol is defined with ".symver foo,foo@VER", the assembler
creates two symbols in the object: one unversioned, and one with
the (non-default) version "VER". If foo is listed in a version
script, gold would then make the first of those symbols the
default version, and would ignore the second symbol as a
duplicate, without making it a non-default version. While this is
arguably reasonable behavior, it doesn't match Gnu ld behavior,
so this patch fixes that by allowing the second definition to
override the first by resetting the "default version" indication.
Several test cases from the Gnu ld testsuite also exposed another
related problem, where a symbol defined with ".symver foo,foo@",
placed into a shared library, is not handled properly by gold.
This patch also fixes that case, binding the symbol to the base
version.
gold/
PR gold/18703
* dynobj.cc (Versions::record_version): Handle symbol defined with
base version.
(Versions::symbol_section_contents): Likewise.
* symtab.h (Symbol::set_is_not_default): New class method.
(Symbol_table::resolve): Add is_default_version parameter.
(Symbol_table::should_override): Likewise.
* resolve.cc (Symbol_table::resolve): Add is_default_version parameter,
and pass to should_override. Adjust all callers and explicit
instantiations.
(Symbol_table::should_override): Add is_default_value parameter;
allow default version in a dynamic object to override existing
definition from same object.
* symtab.cc (Symbol_table::add_from_object): Handle case where same
symbol is defined as unversioned and non-default version in the same
object.
* testsuite/Makefile.am (ver_test_13): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/ver_test_4.cc: Add test for symbol with base version.
* testsuite/ver_test_4.sh: Likewise.
* testsuite/ver_test_13.c: New source file.
* testsuite/ver_test_13.script: New version script.
* testsuite/ver_test_13.sh: New test case.
The gABI allows STT_COMMON symbols to appear in executables and shared
objects, so that the dynamic loader can resolve commons across modules.
When reading a shared object, however, an STT_COMMON symbol should be
treated as a regular definition at link time.
In a relocatable object, the gABI requires that any STT_COMMON symbols
must also be defined in the special SHN_COMMON section (which we extend
to include target-specific small and large common sections). Thus,
there is no need for gold to treat STT_COMMON symbols as common unless
the st_shndx field is also set to a common section.
gold/
PR gold/18288
* resolve.cc (symbol_to_bits): Remove type parameter; adjust all
callers. Don't use STT_COMMON to check for common symbols.
(Symbol_table::resolve): Warn if relocatable object has STT_COMMON
symbol that's not in a common section.
* symtab.h (Symbol::is_common): Don't use STT_COMMON to check for
common symbols.
The plugin API doesn't provide a way for the claimed file handler to
identify a TLS symbol, so when adding a common TLS symbol, gold
mistakenly places the symbol in the non-TLS commons list, and does
not override it when we see the replacement symbol that is marked
as TLS. Consequently, we allocate the TLS common symbol as a regular
common, and, if it's the only TLS in the program, we'll give an
internal error because we haven't allocated a TLS segment.
This patch fixes the problem by removing an exclusion where common
symbols would not override the placeholder symbols, but checking to
see if the size needs adjusting (the original reason for the exclusion).
Furthermore, we need to avoid putting placeholder symbols in the common
list, and wait until we see a real common symbol with a type we can
trust.
gold/
PR gold/17432
* resolve.cc (Symbol_table::resolve): Override common placeholder
symbols, but adjust sizes.
* symtab.cc (Symbol_table::add_from_object): Don't add placeholder
symbols to common lists.
gold/ChangeLog:
2014-09-17 Rafael Ávila de Espíndola <rafael.espindola@gmail.com>
* plugin.cc (Sized_pluginobj::do_add_symbols): Ignore isym->size.
* resolve.cc (Symbol_table::resolve): Don't override common symbols
during the replacement phase.
* resolve.cc (Symbol::override_base): Don't override st_type
from plugin placeholder symbols.
(Symbol_table::resolve): Likewise.
(Symbol_table::should_override): Don't complain about TLS mismatch
if the TO symbol is a plugin placeholder.
* testsuite/Makefile.am (plugin_test_tls): New test.
* testsuite/Makefile.in: Regenerate.
* testsuite/plugin_test_tls.sh: New test script.
* testsuite/two_file_test_2_tls.cc: New test source.
* testsuite/two_file_test_tls.cc: New test source.
* plugin.cc (is_visible_from_outside): Check for symbols
referenced from dynamic objects.
* resolve.cc (Symbol_table::resolve): Don't count references
from dynamic objects as references from real ELF files.
* testsuite/plugin_test_2.sh: Adjust expected result.
* resolve.cc (Symbol_table::should_override): Add fromtype
parameter. Change all callers. Give error when linking together
TLS and non-TLS symbol.
(Symbol_table::should_override_with_special): Add fromtype
parameter. Change all callers.
* i386.cc (Target_i386::Relocate::relocate_tls): Don't crash if
there is no TLS segment if we have reported some errors.
* x86_64.cc (Target_x86_64::relocate_tls): Likewise.
PR gold/12952
* resolve.cc (Symbol::override_base_with_special): Don't override
the version if the overriding symbol has a different name.
* dynobj.cc (Versions::add_def): Add dynpool parameter. Change
all callers. If we give an error about an undefined version,
define the base version if necessary.
* dynobj.h (class Versions): Update declaration.
* testsuite/weak_alias_test_5.cc: New file.
* testsuite/weak_alias_test.script: New file.
* testsuite/weak_alias_test_main.cc: Check that versioned_symbol
and versioned_alias have the right value, and call t2.
* testsuite/Makefile.am (weak_alias_test_DEPENDENCIES): Add
weak_alias_test_5.so.
(weak_alias_test_LDADD): Likewise.
(weak_alias_test_5_pic.o, weak_alias_test_5.so): New targets.
* testsuite/Makefile.in: Rebuild.
* gold/resolve.cc (Symbol_table::should_override): Let a weak
reference override an existing dynamic weak reference.
* testsuite/Makefile.am: Add new test dyn_weak_ref.
* testsuite/Makefile.in: Regenerate.
* testsuite/dyn_weak_ref.sh: New file.
* testsuite/dyn_weak_ref_1.c: Ditto.
* testsuite/dyn_weak_ref_2.c: Ditto.
Doug Kwan <dougkwan@google.com>
* resolve.cc (Symbol_table::should_override): When a weak dynamic
defintion overrides non-weak undef, remember that the original undef
is not weak.
* symtab.cc (Symbol_table::sized_write_global): For undef without
an original weak binding, set binding to global in output.
* testsuite/Makefile.am: Add new test strong_ref_weak_def.
* testsuite/Makefile.in: Regenerate.
* testsuite/strong_ref_weak_def.sh: New file.
* testsuite/strong_ref_weak_def_1.c: Ditto.
* testsuite/strong_ref_weak_def_2.c: Ditto.
weak when resolving to a dynamic def.
(Symbol_table::should_override): Add adjust_dyndef flag; set it
for weak undef/dynamic def cases. Adjust callers.
* symtab.cc (Symbol::init_fields): Initialize undef_binding_set_ and
undef_binding_weak_.
(Symbol_table::sized_write_globals): Adjust symbol binding.
(Symbol_table::sized_write_symbol): Add binding parameter.
* symtab.h (Symbol::set_undef_binding): New method.
(Symbol::is_undef_binding_weak): New method.
(Symbol::undef_binding_set_, Symbol::undef_binding_weak_): New members.
(Symbol_table::should_override): Add new parameter.
(Symbol_table::sized_write_symbol): Add new parameter.
* testsuite/weak_undef_file1.cc: Add new test case.
* testsuite/weak_undef_file2.cc: Fix header comment.
* testsuite/weak_undef_test.cc: Add new test case.
PR 11247
* arm-reloc-property.cc (cstdio): Include.
* configure.ac (targetobjs): Remove duplicates.
* configure: Regenerate.
* resolve.cc (Symbol_table::resolve): Explicit instantiate both
big and little endian version for a given address size.
* symtab.h (class Symbol): Remove fields is_target_special_ and
has_plt_offset_. Add field is_defined_in_discarded_section_.
(Symbol::is_defined_in_discarded_section): New function.
(Symbol::set_is_defined_in_discarded_section): New function.
(Symbol::has_plt_offset): Rewrite.
(Symbol::set_plt_offset): Verify that new offset is not -1U.
* symtab.cc (Symbol::init_fields): Initialize plt_offset_ to -1U.
Don't initialize is_target_special_ or has_plt_offset_.
Initialize is_defined_in_discarded_section_.
(Symbol_table::add_from_relobj): If appropriate, set
is_defined_in_discarded_section.
* resolve.cc (Symbol::override_base_with_special): Don't test
is_target_special_. Change has_plt_offset_ to has_plt_offset().
* target-reloc.h (relocate_section): Do special handling for
symbols defined in discarded sections for global symbols as well
as local symbols.
* options.h (class General_options): Add
--allow-multiple-definition and -z muldefs.
* resolve.cc (Symbol_table::should_override): Don't warn about a
multiple symbol definition if --allow-multiple-definition or -z
muldefs.
* options.h (class General_options): Add --warn-common.
* resolve.cc (Symbol_table::resolve): Handle --warn-common when
merging two common symbols.
(Symbol_table::should_override): Handle --warn-common when merging
a common symbol with a defined symbol. Use report_resolve_problem
for multiple definitions.
(Symbol_table::report_resolve_problem): New function.
* symtab.h (class Symbol_table): Declare report_resolve_problem.
* resolve.cc (Symbol_table::resolve): Check for references from
dynamic objects to hidden and internal symbols.
* testsuite/Makefile.am (hidden_test.sh): New test.
* testsuite/Makefile.in: Regenerate.
* testsuite/hidden_test.sh: New script.
* testsuite/hidden_test_1.c: New test source.
* testsuite/hidden_test_main.c: New test source.
Target::new_output_section.
(Layout::attach_allocated_section_to_segment): Put large section
sections in a separate load segment with the large segment flag
set.
(Layout::segment_precedes): Sort large data segments after other
load segments.
(align_file_offset): New static function.
(Layout::set_segment_offsets): Use align_file_offset.
* output.h (class Output_section): Add is_small_section_ and
is_large_section_ fields.
(Output_section::is_small_section): New function.
(Output_section::set_is_small_section): New function.
(Output_section::is_large_section): New function.
(Output_section::set_is_large_section): New function.
(Output_section::is_large_data_section): New function.
(class Output_segment): Add is_large_data_segment_ field.
(Output_segment::is_large_data_segment): New function.
(Output_segment::set_is_large_data_segment): New function.
* output.cc (Output_section::Output_section): Initialize new
fields.
(Output_segment::Output_segment): Likewise.
(Output_segment::add_output_section): Add assertion that large
data sections always go in large data segments. Force small data
sections to the end of the list of data sections. Force small BSS
sections to the start of the list of BSS sections. For large BSS
sections to the end of the list of BSS sections.
* symtab.h (class Symbol): Declare is_common_shndx.
(Symbol::is_defined): Check Symbol::is_common_shndx.
(Symbol::is_common): Likewise.
(class Symbol_table): Define enum Commons_section_type. Update
declarations. Add small_commons_ and large_commons_ fields.
* symtab.cc (Symbol::is_common_shndx): New function.
(Symbol_table::Symbol_table): Initialize new fields.
(Symbol_table::add_from_object): Put small and large common
symbols in the right list.
(Symbol_table::sized_finalized_symbol): Check
Symbol::is_common_shndx.
(Symbol_table::sized_write_globals): Likewise.
* common.cc (Symbol_table::do_allocate_commons): Allocate new
common symbol lists. Don't call do_allocate_commons_list if the
list is empty.
(Symbol_table::do_allocate_commons_list): Remove is_tls
parameter. Add comons_section_type parameter. Change all
callers. Handle small and large common symbols.
* object.cc (Sized_relobj::do_finalize_local_symbols): Check
Symbol::is_common_shndx.
* resolve.cc (symbol_to_bits): Likewise.
* target.h (Target::small_common_shndx): New function.
(Target::small_common_section_flags): New function.
(Target::large_common_shndx): New function.
(Target::large_common_section_flags): New function.
(Target::new_output_section): New function.
(Target::Target_info): Add small_common_shndx, large_common_shndx,
small_common_section_flags, and large_common_section_flags
fields.
(Target::do_new_output_section): New virtual function.
* arm.cc (Target_arm::arm_info): Initialize new fields.
* i386.cc (Target_i386::i386_info): Likewise.
* powerpc.cc (Target_powerpc::powerpc_info) [all versions]:
Likewise.
* sparc.c (Target_sparc::sparc_info) [all versions]: Likewise.
* x86_64.cc (Target_x86_64::x86_64_info): Likewise.
(Target_x86_64::do_new_output_section): New function.
* configure.ac: Define conditional MCMODEL_MEDIUM.
* testsuite/Makefile.am (check_PROGRAMS): Add large.
(large_SOURCES, large_CFLAGS, large_DEPENDENCIES): Define.
(large_LDFLAGS): Define.
* testsuite/large.c: New file.
* testsuite/testfile.cc (Target_test::test_target_info):
Initialize new fields.
* configure, testsuite/Makefile.in: Rebuild.
Alan Modra
Cary Coutant
H.J. Lu
Yiran Wang
Cary Coutant
Rafael Ávila de Espíndola
Ian Lance Taylor
Doug Kwan
Nick Clifton